1. Field of the Invention
This invention relates to an improvement in a fluid coking process. More particularly, this invention relates to a fluid coking process in which inert solids are added to the chargestock in a specified amount.
2. Description of the Prior Art
Fluid coking is a well known process which may be carried out with or without recycle of the heavier portion of the fluid coking zone effluent. As is well known in the art, the fluid coking process, as shown for example, in U.S. Pat. No. 2,881,130, which is hereby incorporated by reference, uses a fluid coking vessel and an external heating vessel. A fluid bed of solids, preferably coke particles produced by the process having a size in the range from about 40 to about 1000 microns is maintained in the coking zone by the upward passage of fluidizing gas, usually steam, injected at a superficial velocity usually between 0.3 and 5 feet per second. The temperature in the fluid coking bed is maintained in the range of about 850.degree. to about 1400.degree. F., preferably between 900.degree. and 1200.degree. F. by circulating solids (coke) to the heating vessel and back. The heavy oil to be converted is injected into the fluid bed and upon contact with the hot solids undergoes pyrolysis evolving higher hydrocarbon products in vapor phase, including normally liquid hydrocarbons, and depositing a carbonaceous residue (coke) on the solids. The turbulence of the fluid bed normally results in substantially isothermal reaction conditions and thorough and rapid distribution of the heavy injected oil. The feed rate and temperature are controlled to maintain the bed in a fluidized state. Product vapors, after removal of entrained solids, are withdrawn overhead from the coking zone and sent to a scrubber and fractionator for cooling and separation. The end boiling point of distillate fractions obtained from the process is usually about 1050.degree. F. to about 1200.degree. F. and the remaining heavy ends are usually recycled to extinction.
It is also known to add solid particles to the coker feedstock or to subject hydrocarbonaceous oils comprising solid particles to pyrolysis (e.g. coking).
U.S. Pat. No. 3,414,504 discloses recycling coke particles directly to the coker or in admixture with the oil feed.
Canadian Pat. No. 1,070,634 discloses recycling wet coke fines into the coker oil feed.
U.S. Pat. No. 3,278,412 discloses recycling coke-free tar sand fines to a coking zone.
U.S. Pat. No. 3,617,513 discloses recycling coal liquefaction bottoms which comprise unconverted coal, and mineral matter, as feed to a fluid coker.
U.S. Pat. No. 4,075,079 discloses utilizing as coker feed a mixture of fresh coal and coal liquefaction bottoms.
U.S. Pat. No. 4,113,602 discloses blending from about 0.1 to 5 parts by weight of fines derived from gasification of carbonaceous solids and a heavy oil and coking the mixture.
U.S. Pat. No. 4,204,943 discloses a combination of hydroconversion, coking and gasification process. Solids of less than about 10 microns in size such as coke, coal, carbonaceous residue from gasification, are added to the hydroconversion stage. The bottoms of the hydroconversion stage, which comprise solids, are introduced into the coker as feed. See also U.S. Pat. No. 4,178,227.
U.S. Pat. No. 4,169,038 discloses hydroconversion utilizing fines recovered from gasification of coke and introducing the bottoms, including the solids, of the hydroconversion zone into the coker.
U.S. Pat. No. 4,229,283 discloses fluid hydrocoking with the addition of dispersible metal compounds in the coker feed. Metallic ashes recovered from the gasification of the coke are recycled to the coker feed.
U.S. Pat. No. 4,269,696 discloses the addition of cracking catalyst particles to a coker chargestock.
It has now been found that the addition of inert solids to a hydrocarbonaceous oil feed in a specified proportion will permit conducting the fluid coking reaction at a lower temperature at a constant feed rate or will permit an increase in feed rate at a constant temperature.